Whitney returns from the Marines hoping to rekindle a romance with Lana, but Clark is suspicious of his behavior.

The intro: Clark is trying to help Lana fix a leaky pipe at the Talon. When she runs for a wrench and a towel, he uses heat vision to weld the pipe. Lana returns and is treated to the sight of Clark's muscles outlined by his wet t-shirt. Clark hints at missing Lana's visits to the barn, now that she's not a neighbor.

Recap on Whitney: Whitney has been missing for a month. They've even sent his personal belongings to his mom. Lana's worried. Recapping Whitney's character, Lana cried when she learned that Whitney was missing in action in the "Skinwalkers" episode. Lana told Clark that she broke up with Whitney during the "Duplicity" episode. Cut to a combat scene in Indonesia. Whitney and some from his troop wander missing. Enemy shells start to fly in ambush. Whitney helps an injured comrade as an explosion blows up in front of them.

What's up with Lana? At school, Clark asks Lana to a Winterfest. She accepts. Just then, in walks Whitney in his dress uniform. Lana runs to his arms. Later, Whitney tells Lana an explosion in an ambush wiped out part of his memory. He has conveniently forgotten her "dear john" breakup video message. Lana hosts a welcome home party for Whitney at the Talon. Whitney seems jealous when he sees Clark and Lana talking, although she says she and Clark are just friends. Whitney throws an enraged jealous fit in the bathroom, tearing off a door. Clark walks in on the scene. Whitney warns Clark to stay away from Lana. Then Whitney reverses the story to Lana, telling her that Clark destroyed the bathroom and told Whitney to stay away from her.

What's up with Whitney? A Marine officer comes to the Fordman home with news. Whitney runs downstairs and beats the officer to death with a baseball bat, then muffles his mother's screams. He turns into a total freak at home, threatening his mother, binding and gagging her. Whitney asks Lana to move in together. She refuses. He blames Clark.

What's up with Lex? After five dates, Lex confronts Dr. Helen Bryce (Emmanuelle Vaugier). She says she never met Lionel, yet Lex has surveillance photos of her meeting him. He had a private investigator following Lionel. After further digging, he also found $100,000 in her bank account from LuthorCorp. Helen is furious with his invasion of her privacy. Lex tells Clark about Helen's suspected espionage. Clark suggests he talk to her, and maybe it was a misunderstanding. Clark tells Lex about Whitney's bizarre behavior. Lex thinks Whitney is suffering from post traumatic stress disorder, and suggests a specialist in Metropolis. Later Lex finds Helen at the Talon. She gives the explanation that Lionel offered her money to dump Lex. She refused, but he wired the money to her account anyway. She's still angry and won't take Lex back. Finally Lex visits Dr. Helen at work at the hospital, spilling his feelings about his past and how he's built a wall around his heart to protect his feelings. He asks for Helen's help. She takes his hand and they walk away together.

What's up with Clark? Clark visits Whitney's home to suggest he get treatment for post traumatic stress disorder. Whitney throws Clark to the ground. Clark's x-ray vision sees the effects of green kryptonite in Whitney's body. He suspects Tina Grier (X-ray episode, season 1) has shape-shifted and is impersonating Whitney. She was always obsessed with Lana. Chloe says Tina committed suicide last week. Clark asks Pete to stay with Lana, and tells Lana that Whitney is really Tina. After Clark leaves, Lana (Tina) throws Pete into the lockers, leaving him unconscious.

How it ends: Whitney proposes to Lana, wanting to elope. He asks her with his mom's ring. Lana can't accept, and tells him they are really broken up. Whitney (Tina) asks Lana for her necklace to remember her by.

Back at Clark's house, his dad asks about Mrs. Fordman and Whitney. We see that Jonathan has Lana's necklace, and is really shape-shifted Tina. Tina puts the necklace around Clark's neck, making him powerless. She throws him into the cellar and ties him up. She tells him she wants to be with Lana. Tina shape-shifts into Clark and goes off to get Lana. Clark struggles in the cellar. His spaceship activates from the corner, draining the green color from the stone in the necklace. The necklace is no longer a threat, and Clark frees himself. Back at Chloe's house, Tina impersonates Chloe. She touches Lana, making her flinch, feeling uncomfortable.

Next at the Talon, Clark (Tina) tells Lana he loves her. They kiss. The real Clark interrupts. Clark (Tina) throws Lana aside. During a fight between Clark and Clark (Tina), Tina impales herself.

Later Clark shares the news with his parents that the Marine that Tina murdered at the Fordman house was coming to tell Mrs. Fordman that Whitney's body was found. Clark questions his own courage at the news of Whitney's loss.

Later Lana finds Clark alone in the cave. She feels sorry for Whitney's death, and blames herself. She's lost all those she's cared about; her parents, Nell, now Whitney. Lana tells Clark she doesn't want to lose him too. He tells her he's not going anywhere. They embrace.